AstroAlertBench: Evaluating the Accuracy, Reasoning, and Honesty of Multimodal LLMs in Astronomical Classification. - Claire Chen; Jiabao Sean Xiao; Shuze Daniel Liu; Facundo Perez Paolino; Luke Handley; Theophile Jegou du Laz; Ricky Nilsson; Alice Zou; Matthew J. Graham; Ashish Mahabal (CoRR, 2026)